Lymphography was used to investigate nine patients who presented with chylothorax after surgery of the thorax. Leakage of the lipiodol was identified from the thoracic duct in six patients and from tributaries of the thoracic duct in two patients. There was complete occlusion of the thoracic duct at the site of injury in two patients but leakage could not be visualized at the time of the procedure. The different methods of treatment of chylothorax and the influence of the lymphographic findings on management are discussed.